Q&A - PSLE Science

[chrisu]

It's alright Tianzhu. I will get my daughter to check with the teacher.


I understand why most ppl choose (2) as answer; It is true that total current flow to that junction equal to the sum of both flowing out. IT = Ir + IR;
http://img.photobucket.com/albums/v160/guppiesonli/Misc/Calculating.jpg\">

Let us not forget that when Switch A is closed, the wire resistance is probably very low (can assume to be 0.0001ohm). You may read here for http://www.furryelephant.com/content/electricity/resistance-ohms-law/.

So the total resistance of the wire (when switch A closed) and bulb (assume to be 10ohm) in parallel = 0.0000099 ohm.
Total resistance in circuit = 10 + 0.0000099 = 10.0000099 ohm.
Therefore total current IT = 3/10.0000099 = 0.2999997 A

Voltage across the first bulb connected nearest to battery = IT x 10 ohm
= 0.2999997 x 10 = 2.999997V

As you can see, most of the 3V battery is dropped across this bulb (2.999997V) and very very little voltage across the other bulb - thus the voltage is not high enough to light up that bulb.

tianzhu:

Hi Chrisu

Thank you for carrying out the experiment. This means none of the possible answers given in the test paper is correct.

http://img.photobucket.com/albums/v160/guppiesonli/Misc/P6-Sc.jpg

I apologise for leading you the wrong way.

You may wish to check with your kid’s teacher for the right answer.

Best wishes

[atutor2001]

Hi Chrisu


I didn't pay attention to the question till you posted your illustrations and experiments.

You have very good electrical knowledge. Many will have great difficulty visualising the short-circuit caused by switch A on bulb B - few will know how to flip switch A down like you did in your diagram. I believe the pr sch teacher who set the question didn't realise that too. There are many such mistakes in Pr Sc questions. Yes, you are absolutely correct, none of the circuits fit the results given.

Your child is very lucky to have a parent like you.

Cheers.

ps

Just saw your latest circuit diagram. You are guaranteed electrical engineering trained.

[pixiedust]

Oh dear! I just revised electricity but I am seeing even more stars now! Chrisu, agree your child is really lucky! Appreciate to know (1) where in sim lim to get the experiment kits? (2) please update us when the teacher response regarding the question, thanks very much.


To all : about short circuit - is it not in psle syllabus? I came across one oe question in p5 process skills assessment book and also one paragraph explanation in mc psle science guide.

[chrisu]

Thanks atutor2001. I've studied Electronics in poly many years back (70s) and have forgotten most of it.


I remember I've taught my eldest son in sec.4 last year on bulb brightness in series and parallel circuit (one of those favourite topic in school) and some other bulb questions, and now my daughter P6 also learning the same thing in the worksheet and test.

Primary school text book and what teacher taught are always very brief but the exam and test or worksheet are very difficult.

atutor2001:

Hi Chrisu

I didn't pay attention to the question till you posted your illustrations and experiments.

You have very good electrical knowledge. Many will have great difficulty visualising the short-circuit caused by switch A on bulb B - few will know how to flip switch A down like you did in your diagram. I believe the pr sch teacher who set the question didn't realise that too. There are many such mistakes in Pr Sc questions. Yes, you are absolutely correct, none of the circuits fit the results given.

Your child is very lucky to have a parent like you.

Cheers.

ps

Just saw your latest circuit diagram. You are guaranteed electrical engineering trained.

[chrisu]

I bought it from the shop selling electronic components faching the escalator (2nd floor). Sim Lim the one selling electrical appliances and components (not the one selling computer stuff). Near to Sungei Rd that Sim Lim. It's not a kit, just buy some bulbs and wire.


Will update once the teacher get back to us.

Primary school probably won't use the term short circuit but they have to know how to connect a bulb to the battery source correctly.

pixiedust:

Oh dear! I just revised electricity but I am seeing even more stars now! Chrisu, agree your child is really lucky! Appreciate to know (1) where in sim lim to get the experiment kits? (2) please update us when the teacher response regarding the question, thanks very much.

To all : about short circuit - is it not in psle syllabus? I came across one oe question in p5 process skills assessment book and also one paragraph explanation in mc psle science guide.

[atutor2001]

I remembered short circuit did come out in PSLE. If I am not wrong, Pr students are expected to know that electricity will "flow through the path that has the least resistance i.e. obstacle".

[P5G]

Please help.


http://www.orlesson.org/orp/10Sc/2010-P6-Sc-SA2-Nanyang.pdf


Question 18 - Energy
Worksheet answer is (1). Should the correct answer be (2)?


Question 21 - Electricity
Worksheet answer is (1). Should the correct answer be (2)?


TIA.

[Hifive]

Hi all


Please help with this question:

http://www.flickr.com/photos/62186744@N04/6028721608/

Thanks in advance!

[IMTRYINGSTUFF]

[quote=\"Hifive\"]Hi all


Please help with this question:

http://www.flickr.com/photos/62186744@N04/6028721608/

Thanks in advance![/q
b.)The magnetic force of attraction is no longer present and so the sphere is no longer attracted to the toy. The sphere then is pulled by gravity and falls to the ground.
c.) No, it cannot. Steel is a magnetic material, so it prevents the magnetic force of attraction from passing through. The sphere will not be able to be attracted to the toy and so he toy would not work.

I think these are the answers in the view of a P6 student

[atutor2001]

Hifive:

Hi all


Please help with this question:

http://www.flickr.com/photos/62186744@N04/6028721608/

Thanks in advance!

This is a good example of how irresponsible primary sc dept can be. It is common knowledge that without any restraint to hold back the ball, it will be attracted to the \"toy\" (inverse square law). It will not remain floating in the air as claimed. Therefore, the situation as shown in the question cannot happen... or did I miss something new that is being thought nowadays.